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payloadType

There are currently five four payload types defined and three reserved:. The rest are reserved.

PT_DATA = 0

A regular data fragment. The payload is a binary blob.

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A request to the server to open a new session or a response from the server for
such a request. The payload must be empty for a session open request (for now)
and is defined below for a session open response.

PT_RESERVED_1 = 3

Reserved for future use.

PT_BAD_SESSION = 4

A response from the server that the session specified is not valid. The payload
must be empty.

PT_RETRY_WITH_NEW_RPCID = 5

A response from the server that it has discarded its state for the rpcId
specified (but the session is still valid). The payload must be empty.

PT_RESERVED_2 = 6

Reserved for future use.

PT_RESERVED_3 = 7

Reserved for future use.

sessionToken

The session token serves to identify the session. It is large enough that it
can be generated randomly with a very low probability of collisions.

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The RPC ID serves to ensure that old packets on a channel that is still valid
are ignored. The client may must start the RPC ID with any value 0 on a new channel (0
is a reasonable choice), and must
increment it on every new RPC that it sends
over the channel.

fragNumber

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Connections are automatically closed a machine when it detects that the
connection has been idle for a long time. Error packets are generated when
packets are received containing a connection id for one that has been closed.

Questions/Comments

Should the request and reply flags be replaced with a single direction flag?

Should a newly opened connection ID come back as a well-formed control packet with its own control packet opcode?

The server's history list is not sufficient. Do we need it?

For example, read responses will use large amounts of memory and take very little work to recreate.

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